1. Field of the Invention
The present invention relates to a thin film magnetic head equipped with a magnetic conversion element, and a manufacturing method thereof, as well as a head gimbal assembly, a head arm assembly, and a magnetic disk device, each of which is equipped with a thin, film magnetic head.
2. Description of the Related Art
Conventionally, a magnetic disk device has been used as one for performing write and read of magnetic information (hereinafter referred to simply as information). The magnetic disk device has, within a casing, for example, a magnetic disk where information is stored, and a thin film magnetic head for performing write of information into the magnetic disk and read of information written in the magnetic disk. The magnetic disk is supported by a rotation shaft of a spindle motor fixed to the casing, and is rotated about the rotation shaft. On the other hand, the thin film magnetic head is formed on one side surface of a magnetic head slider provided at one end of a suspension, and includes a magnetic write element and a magnetic read element each having an air bearing surface (ABS) opposed to the magnetic disk. In particular, as a magnetic read element, an MR element exhibiting magnetoresistive (MR) effect is generally used. The other end of the suspension is fixed to a tip of an arm supported rotatably by a fixed shaft.
Meanwhile, in the recent years, as the tendency of high density writing (the tendency of large capacity) of magnetic disks is advanced, the tendency of a reduction in write track width is advanced. As the write track width is narrower, the dimension of the thin film magnetic head is smaller. Thus, the signal write capability of the magnetic write element into the magnetic disk is weakened, and the strength of a signal magnetic field from the magnetic disk is also weakened. In order to compensate for deterioration in these functions, it is required to generate a stronger write magnetic field, and further reduce magnetic spacing (bring the ABS of the thin film magnetic head close to the magnetic disk surface).
To this end, it can be considered, for example, to pass greater write current during the time of information write operation. However, when large current is passed, the thin film magnetic head itself generates heat, so that expansion toward the magnetic disk, so-called thermal protrusion may take place. If the thermal protrusion occurs, there is the risk of lack of reliability as a magnetic write device.
A large number of techniques of suppressing the occurrence of thermal protrusion have been reported so far. Firstly, for example, in Japanese Unexamined Utility Model Application Publication No. Hei 2-101308, Japanese Unexamined Patent Application Publications Nos. 2004-2203, 2004-362660, and 2003-91802, it is disclosed to suppress the occurrence of thermal protrusion in the following manner that heat dissipation properties are improved by disposing a heat dissipating layer formed of metal on a magnetic layer (a first manner). Secondly, for example, in the specification of U.S. Pat. No. 6,842,308 and the specification of U.S. Pat. No. 6,989,963, it is disclosed to suppress the occurrence of thermal protrusion in the following manner that heat dissipation properties are improved by disposing a heat dissipating layer formed of material having a large thermal conductivity so as to cover a thin film coil for generating a magnetic flux (a second manner). Thirdly, for example, in “On the Thermal Behavior of Giant Magnetoresistance Heads” B. K. Gupta, Kenneth Young, Samerra K. Chilamakuri, Aric K. Menon, p. 380-387, vol. 123, April 2001, or the like, it is disclosed to suppress the occurrence of thermal protrusion in the following manner that a thermal expansion suppressing layer formed of material, having a small coefficient of thermal expansion and a large thermal conductivity, is disposed directly on a magnetic layer in order to improve heat dissipation properties and also suppress the magnetic layer and the like from shifting toward a magnetic disk (a third manner). Fourthly, for example, in Japanese Unexamined Patent Application Publication No. 2005-285236, it is disclosed to suppress the occurrence of thermal protrusion in the following manner that a thermal expansion suppressing layer similar to the above is disposed on a magnetic layer with a protective layer formed of alumina in between, in order to prevent the magnetic layer and the like from shifting toward a magnetic disk (a fourth manner).